The global impact of stellar winds and supernovae on the interstellar medium

The interstellar medium is an extremely heterogeneous mixture of gas and dust which fills the space between stars in galaxies. The life-cycle of stars is deeply connected with the presence of this medium. Massive stars form from very high density/low temperature gas and evolve for millions of years. They emit ionising radiation, blow powerful winds from their surface and, at the end of their \nlifetime, explode as supernovae, thereby heating up and compressing the surrounding material. These stellar feedback processes are fundamental, since they are able to influence the evolution of the interstellar medium at different scales and eventually to promote or deter further star formation events. In this thesis, we investigate the impact of stellar winds and supernovae on the interstellar medium by performing three-dimensional, Adaptive-Mesh-Refinement, hydrodynamic simulations at intermediate (pc-kpc) scales. We study how different assumptions on the position of supernova explosions drive completely different properties of the gas within disc galaxies. Supernovae are placed either at random positions, in density peaks, or both. Explosions located in density peaks do not produce hot gas due to large radiative losses and atomic hydrogen dominates the mass. Random supernovae create a large volume filling hot phase that compresses the gas into small clumps and the majority of the mass is in the form of molecular hydrogen. We then show how the combination of stellar winds and supernovae is able to regulate the otherwise over-efficient star formation process. We model star formation self-consistently via sink particles and we demonstrate how stellar winds are able to reduce the amount of gas converted into stars both at local and global scales. The inclusion of supernovae produce a hot, over-pressurised phase responsible for outflows launching.